#./lib/my_module.rb

# Dynamically create nested modules
def register_module(module_name)
  module_names = module_name.split("::").inject([]) { |n, c| n << (n.empty? ? [c] : [n.last] + [c]).flatten }
  module_names.each do |module_name_array|
    *prefix, parent, child = module_name_array
    if child
      full_path_child_module_name = module_name_array.join("::")
      if Object.const_defined?(full_path_child_module_name)
        puts "full_path_child_module_name: #{full_path_child_module_name} -> defined"
      else
        puts "full_path_child_module_name: #{full_path_child_module_name} -> not defined yet"
        parent_module = find_or_register_module(parent, prefix)
        parent_module.const_set child, Module.new
      end
    else
      find_or_register_module(parent, prefix) # register parent_module
    end
  end
end

def find_or_register_module(name, prefix)
  full_path_module_name = (prefix + [name]).join("::")
  if Object.const_defined? full_path_module_name
    Object.const_get full_path_module_name
  else
    if prefix.empty?
      Object.const_set name, Module.new
    else
      full_path_prefix = prefix.join("::")
      prefix_module = Object.const_get(full_path_prefix)
      prefix_module.const_set name, Module.new
    end
  end
end

require 'spec_helper'
require './lib/my_module'
RSpec.describe do
  context do
    let(:module_name) { "Abc123::Foo::Bar" }
    before do
      register_module("Bar")
      register_module(module_name)
    end
    it { expect(Object.const_get(module_name)&.to_s).to match(module_name) }
  end
end